Pile foundation structure

ABSTRACT

The present invention relates to a technique wherein a complex structure is adopted as a joint structure between each head of plural piles ( 1 ) and a bottom of a footing ( 2 ), and the complex structure may be selected among either a complex of a roller bearing structure (Y) interposing a sliding member ( 12 ) and a pin bearing structure (X) interposing a sliding member ( 32 ), another complex of a rigid joint structure (Z) and the roller bearing structure (Y), or still another complex of the rigid joint structure (Z) and a pin bearing structure (X). This can restrain the rotation of an upper structure (A), reduce stress concentration applied to a joint portion and occurrence of a bending moment on the pile ( 1 ) in applying a great external force such as an earthquake thereto, prevent damages or destroys of the joint portion and the pile, and also enhance excellent positional restoration performance for restoring the upper structure (A) to an initial position thereof, after the earthquake happens.

TECHNICAL FIELD

The present invention relates to a pile foundation structure forsupporting a footing serving as a foundation of a large-scaled and heavyupper structure such as a high building, and propagating a load of theupper structure to the underground depths by means of plural pointbearing piles or friction piles disposed within a construction range ofthe upper structure so as to be spaced from each other, and driven intothe undergrounds such as a solid rock.

BACKGROUND ART

Such a pile foundation structure is conventionally known, such as thestructure illustrated in FIGS. 11 and 12. In other words, it has astructure wherein plural point piles or friction piles 100 (hereinaftercalled piles) disposed within a construction range (shown by the outlinethereof) of an upper structure A so as to be spaced from each other, isdriven into the underground B, such as solid rock, and a head of theeach pile 100 i.e., a pile head is buried into a foundation 101(hereinafter called a footing) on a side of the upper structure A,whereby the pile 100 is rigidly joined to the footing 101.

FIG. 13 illustrates in detail a joint structure between each pile 100 asa structure element and the footing 101. A lower end ofthe footing 101is mounted on a head of the pile 100, and the pile 100 is rigidlyjointed to the footing 101 by reinforcing steel members 102 including apile reinforcement and a concrete-reinforcing bar, and concrete.

As mentioned above, the conventional pile foundation structure isconstructed so that each pile foundation has the pile 100 rigidly joinedto the footing 101 so that it is longitudinally and laterally disposedwithin the construction range ofthe upper structure A, so as to beappropriately spaced from each other. In case of the conventional pilefoundation structure, earthquake motion which is propagated from theunderground B when an earthquake happens, is input to the upperstructure A via a rigid joint portion between the head ofthe pile 100and the footing 101. In this moment, it is not only that a stress suchas a shear force is concentrated on the joint portion of the head ofeach pile as a boundary portion between both of them, but also that,even if joint between heads of the piles 100 and the footing 101 isperfect, a great bending moment happens on the pile 100 in theunderground B. As a result, the joint portion between the pile head andthe footing 101, and the pile 100 are easily damaged and destroyed.Thus, it is extremely difficult and requires a long period and hugecosts to conduct a restoration construction in case that damage ordestruction is caused on the pile 100, and the joint portion between thepile head and the footing 101.

In order to resolve the above problems, the pile foundation structureemploying a sliding structure is suggested in a gazette of publishedJapanese Patent Application Laying-Open No. 1-102124.

In other words, the pile foundation structure shown in FIG. 14 isstructurally described below. A number of steel reinforcement members103 annularly disposed on an upper end of the pile 100, and steel pipes104 disposed so as to surround the steel reinforcement members 103 in astate of allowing lateral movement of the steel reinforcement members103 are upwardly extended. At each lower end portion of the steel pipes104, annular engagement projections 105 are arranged so as to beconnected to an upper end portion of the pile 100 in a buried state.Moreover, a top board 106 is welded to the upper end portion of thesteel pipes 104, the top board 106 is provided with flexible holes 107for making the steel reinforcement members 103 pierce the top board 106so as to respectively allow lateral shaking of the steel reinforcementmembers 103. The steel reinforcement members 103 protruding above thetop board 106 through the flexible holes 107, are connected to thefooting 101 of the upper portion thereof. Furthermore, there is asliding member 109 between the top board 106 and a footing metal member108, through which the footing 101 is slidably mounted on the top board106.

In the pile foundation structure having such a sliding arrangement, whenthe earthquake motion is applied, the steel reinforcement members 103are bent, and at the moment while they are bent, the sliding member 109makes the footing 101 slidingly move with respect to the pile 100,thereby making it possible to restrict stress concentration on the jointportion of the pile head. However, the sliding amount is regulated bythe size of each flexible hole 107 disposed on the top board 106, andthe pile 100 is connected to the footing 101 by the steel reinforcementmembers 103 whereby the shearing force and the bending moment cannot beefficiently absorbed in case of applying the excess earthquake motion.Consequently, it is unavoidable that the joint portion between the headofthe pile 100 and the footing 101 is damaged or destroyed. In the sameway as the conventional pile foundation structure in FIG. 13, there hasbeen a problem wherein earthquake-proof property and earthquakeavoidable property cannot be ensured enough.

SUMMARY OF THE INVENTION

The present invention has been conducted in view of the above mentionedcircumstances, i.e., the background of the prior art. Objects of thepresent invention are to provide a pile foundation structure which canreduce stress concentration applied to a joint portion of a pile headand a bending moment applied to the pile which are accompanied withearthquake motion; make a whole of a structure lightweight; reducecosts; prevent the pile and the joint portion of the pile head frombeing damaged or destroyed; and also enhance excellent positionalrestoration performance of an upper structure after the earthquakehappens.

A first aspect of the invention relates to a pile foundation structurefor joining a footing of an upper structure to heads of plural piles (orpile heads) disposed within a construction range of the upper structureso as to be spaced from each other, and driven into the underground,characterized in that

a roller bearing structure is constructed as each joint structurebetween some of the plural piles and portions of the footing of theupper structure corresponding thereto, wherein

a protrusive-supporting-portion having a flat top surface is disposed ona side of the pile head, in a state of protruding above an upper surfaceof the underground,

a recessed-joint-portion having a flat top surface is disposed on a sideof the footing of the upper structure, so as to correspond to theprotrusive-supporting-portion and be greater than theprotrusive-supporting-portion, and

a sliding member is interposed between the top surfaces of theprotrusive-supporting-portion and the recessed-jointing-portion,

thereby making it possible to relatively slidingly move a joint portionof the head of the pile in a horizontal direction; and

a pin bearing structure is constructed as each joint structure betweenthe others of the plural piles and portions of the footing of the upperstructure corresponding thereto, wherein

a spherical-supporting-portion having a convex or concave outer surfaceis disposed on a side of the pile head, in a state of protruding abovethe upper surface of the underground,

a spherical-joint-portion having a concave or convex inner surface isdisposed on a side of the footing of the upper structure, so as tocorrespond to the spherical-supporting-portion and be greater than thespherical-supporting-portion, and

a sliding member is interposed between the outer surface of thespherical-supporting-portion and the inner surface of thespherical-joint-portion of the footing of the upper structure,

thereby making it possible to relatively slidingly rotate the jointportion of the head of the pile.

According to the first aspect of the present invention having such anarrangement, the earthquake motion which is propagated from theunderground when the earthquake happens, is input to the upper structurevia the each supporting portion of the roller bearing structure and thepin bearing structure in each head of the plural piles. In this time, ahorizontal component of the earthquake motion is mainly absorbed by asliding effect of the roller bearing structure wherein theprotrusive-supporting-portion is disposed on a side of the pile head,and the recessed-jointing-portion is disposed on a side of the footing,and the sliding member is interposed between the flat top surfaces ofthe protrusive-supporting-portion and the recessed-jointing-portion,which are opposed to each other. This makes it possible to decrease thestress concentration applied to the joint portion of the pile head and abending moment which occurs on the pile driven into the underground. Onthe other hand, though the upper structure is easily rotated when agreat external force such as the earthquake motion is applied to theupper structure, the rotation of the upper structure can be restrainedby means of the pin bearing structure wherein thespherical-supporting-portion is disposed on the pile head, thespherical-jointing-portion is disposed on the footing, so as tocorrespond thereto, and the sliding member is interposed between theouter surface of the spherical-supporting-portion and the inner surfaceof spherical-jointing-portion. Moreover, the pin bearing structure canensure the positional restoration performance of the upper structureafter the earthquake happens.

As mentioned above, the joint portion between the each head of theplural piles and the footing of the upper structure is built as acomplex structure of the roller bearing structure which is excellent inthe absorbing property of absorbing horizontal shakes, and the pinbearing structure which is excellent in the absorbing property ofabsorbing vertical shakes, and rotation restraint property. Thisstructure can prevent the pile itself and the joint portion of the pilehead from being damaged and destroyed, thereby making it possible todecrease an amount of an arrangement of reinforcement used for the pileand footing, make a whole of the structure lightweight, reduce costs,and exhibit the excellent earthquake avoidable property.

In case of employing the pile foundation structure having such a complexstructure, especially, the structure which includes the roller bearingstructure disposed within the construction range of the upper structure,and the pin bearing structure disposed on an outer periphery of theroller bearing structure, the external force such as the earthquakemotion is applied thereto, with the result that the pin bearingstructure restrains the horizontal movement of the upper structure on aside of the outer periphery of the roller bearing structure whose amountof the horizontal movement is greater than that of the portion supportedby the roller bearing structure, which allows horizontal slidingmovement of the upper structure. This can further improve the positionalrestoration performance of the upper structure after the earthquakehappens.

A second invention of the present application relates to a pilefoundation structure for jointing a footing of an upper structure toheads of plural piles disposed within a construction range of the upperstructure so as to be spaced each other, and driven into theunderground, characterized in that

a rigid joint structure employing reinforcing steel material andconcrete is constructed as each joint structure between some of theplural piles and portions of the footing of the upper structurecorresponding thereto; and

a roller bearing structure is constructed as each joint structurebetween the others of the plural piles and portions of the footingcorresponding thereto, wherein

a protrusive-supporting-portion having a flat top surface is disposed ona side of the pile head, in a state of protruding above an upper surfaceof the underground,

a recessed-jointing-portion having a flat top surface is disposed on aside of the footing of the upper structure, so as to correspond to theprotrusive-supporting-portion and be greater than theprotrusive-supporting-portion, and

a sliding member is interposed between the top surfaces of theprotrusive-supporting-portion and the recessed-jointing-portion,

thereby making it possible to relatively slidingly move a joint portionof the head of the pile in a horizontal direction.

Accordingly, in the second embodiment having such a structure, in casethat the external force such as the earthquake motion propagated fromthe underground is applied to the upper structure when the earthquakehappens, the rigid joint structure between the pile head and the footingcontrols the rotation of the upper structure. Moreover, when the greathorizontal component accompanied with the earthquake motion or the likeis applied thereto, the horizontal component is absorbed by means of thesliding effect of the roller bearing structure, thereby making itpossible to decrease the stress concentration applied to the jointportion of the pile head and the bending moment occurring on the pile.As a result, when the great external force such as the earthquake motionis applied thereto, it is possible to prevent the joint portion of thepile head and the pile itself from being damaged and destroyed, and toexhibit the excellent earthquake avoidable property.

The pile foundation structure according to such a complex structureincluding the rigid joint structure and the roller bearing structure,may have either an arrangement wherein the roller bearing structure isdisposed within the construction range of the upper structure, and therigid joint structure is disposed on a side of the outer periphery ofthe roller bearing structure, or an arrangement wherein the rollerbearing structure is disposed within the construction range of the upperstructure, and the rigid joint structure is disposed on a side of theinner periphery of the roller bearing structure. However, the formerarrangement is more preferable. Namely, in case of the formerarrangement, the external force such as the earthquake motion is appliedthereto, with the result that the rigid joint structure restrains thehorizontal movement of the upper structure on a side of the outerperiphery of the roller bearing structure whose amount of the horizontalmovement is greater than that of the portion supported by the rollerbearing structure, which allows horizontal sliding movement of the upperstructure. This can prevent livability from worsening owing tounnecessary rocking of the upper structure, even if relatively smallexternal forces such as a traffic vibration and a wind load are usuallyapplied thereto. Moreover, when the great external force such as theearthquake motion is applied thereto, this can further exhibit thedamage and destroy prevention functions for preventing the pile and thejoint portion of the pile head from being damaged and destroyed.

A third invention of the present application relates to a pilefoundation structure for jointing a footing of an upper structure toheads of plural piles disposed within a construction range of the upperstructure so as to be spaced each other, and driven into theunderground, characterized in that

a rigid joint structure employing reinforcing steel material andconcrete is constructed as each joint structure between a pile disposedon a side of the center of the construction range of the upperstructure, among the plural piles, and a portion of the footingcorresponding thereto; and

a pin bearing structure is constructed as each joint structure betweenpiles disposed on the outer periphery of the construction range of theupper structure and the footing of the upper structure, wherein

a spherical-supporting-portion having a convex or concave outer surfaceis disposed on a side of the pile head, in a state of protruding abovethe upper surface of the underground,

a spherical-jointing-portion having a concave or convex inner surface isdisposed on a side of the footing of the upper structure, so as tocorrespond to the spherical-supporting-portion and be greater than thespherical-supporting-portion, and

a sliding member is interposed between the outer surface of thespherical-supporting-portion and the inner surface of thespherical-jointing-portion of the footing of the upper structure,

thereby making it possible to relatively slidingly rotate a jointportion of the head of the pile.

In the third embodiment having such an arrangement, in case that theexternal force such as the earthquake motion propagated from theunderground is applied to the upper structure when the earthquakehappens, the rigid joint structure between the pile head and the footingrestrains the upper structure from rotating. When the external forcewhich is above the predetermined value is applied thereto by theearthquake motion or the like, the stress is released by slidingrotation of the pin bearing structure, thereby making it possible todecrease the stress concentration applied to the joint portion of thepile head and the bending moment occurring on the pile. This can preventthe joint portion of the pile head and the pile itself from beingdamaged and destroyed. Moreover, the underground is horizontally moved,there by moving the center of the gravity of the upper structure. As aresult, deformation occurs on the pile in which the rigid jointstructure is adopted, and vertical motion of the upper structure occursaccording to the rotation of the pile head, which is built as the pinbearing structure. Consequently, the structure can ensure the positionalrestoration performance of the upper structure after the earthquakehappens.

In the each pile foundation structure according to the first to thirdinventions having the above structures, a caulking compound isstructurally enclosed with a sliding surface between thesupporting-portion of the pile head and the jointing-portion of thefooting. The caulking compound enclosed with the sliding surface betweenthe supporting-portion of the pile head and the jointing-portion of thefooting can enhance the vibration absorption property, and prevent waterfrom intruding from the outside to the sliding surface. Accordingly,corrosion of a steel material as a structural element is decreased, anddeterioration of the sliding member is decreased, thereby keepingsliding movement and sliding rotation properties caused by the slidingmember smooth and stable for a long period as effects thereof.

Furthermore, the each pile foundation structure according to the firstto third inventions has an arrangement wherein metal parts made of metalare respectively closely fitted into the outer surface of thesupporting-portion of the head of the each pile and the inner surface ofthe jointing-portion of the footing, and the metal parts are integrallyconnected to the head of the pile and the bottom of the footing viaanchor members. Then, the arrangement can have the effects of surelypreventing damage and destroy of the pile head and the footing, andkeeping predetermined sliding movement and sliding rotation propertiessmooth and stable.

In addition, according to the each pile foundation structure accordingto the first to third inventions having the above structures, a materialhaving self-lubricative property is employed as the sliding member.Therefore, even in case that this is the first time that the structure,wherein a long time passed since the execution of the structure, hasundergone the external force such as the earthquake, the predeterminedsliding movement and sliding rotation properties are ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a whole of a pile foundationstructure in a first embodiment of the present invention.

FIG. 2 is a schematic plan view of the pile foundation structureaccording to FIG. 1.

FIGS. 3 and 4 are respectively enlarged longitudinal sectional views ofa main portion showing the pile foundation structure in the firstembodiment of the present invention.

FIGS. 5 to 7 are respectively whole schematic plan views showingmodifications of the pile foundation structure according to the firstembodiment of the present invention.

FIG. 8 is a schematic plan view of a whole of the pile foundationstructure in a second embodiment of the present invention.

FIG. 9 is a whole schematic plan view showing a modification of the pilefoundation structure in the second embodiment of the present invention.

FIG. 10 is a schematic plan view of a whole of a pile foundationstructure in a third embodiment of the present invention.

FIG. 11 is a whole schematic side view showing a general pile foundationstructure according to the prior art.

FIG. 12 is a schematic plan view of the pile foundation structure shownin FIG. 11.

FIG. 13 is an enlarged longitudinal sectional view of a main portion ofthe general pile foundation structure according to the prior art.

FIG. 14 is an enlarged longitudinal sectional view of a main portionshowing a pile foundation structure already suggested in the prior art.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS OF THE PRESENT INVENTION

A first embodiment will be described. As shown in FIGS. 1 and 2, thereare plural point supporting piles or friction piles 1 (hereinaftercalled piles) disposed within a construction range of an upper structureA (shown by the outline of the structure), so as to be spaced betweenthe piles, which are driven into the underground B. such as solid rock.As a joint structure between each head of the piles 1 disposed on anouter periphery of the construction range thereof and a footing 2 of theupper structure A, each pin bearing structure X as shown by a circlewith slant bars in FIG. 2 is adopted. On the other hand, as a jointstructure between each head of the piles 1 disposed on the center of theconstruction range thereof and the footing 2 of the upper structure A, aroller bearing structure Y as shown by a square in FIG. 2 is adopted.

The roller bearing structure Y is constructed as shown in FIG. 3. Inother words, a pile foundation structure shown in FIG. 1 has anarrangement wherein a head of the long pile 1 (or a pile head) made ofreinforced concrete is provided with a columnarprotrusive-supporting-portion 3 having a flat top surface so as toprotrude above an upper surface of the underground B. A pile metal part4 made of a protrusive-seat-shaped metal (mainly steel) correspondingthereto is closely fitted into an outer surface of theprotrusive-supporting-portion 3 of the pile head. Additionally, an innersurface of the pile metal part 4 is integrally fixed and connected tothe head of the pile 1 via a number of anchor members made of steel, forfixation.

A mortar seat 6 and a crushed-stone layer 7 for supporting the footing 2so as to be movable in a horizontal direction, are laminated on an uppersurface of the underground B. A portion corresponding to the head of thepile 1, in the crushed-stone layer 7 and a bottom of the footing 2 madeof reinforced concrete, mounted on the head of the pile 1, is providedwith a cylindrical recessed-jointing-portion 9 having a flat top surfaceso as to correspond to the protrusive-supporting-portion 3 and have agreater diameter than that of the protrusive-supporting-portion 3.

The footing 2 is not linked to the pile 1 by reinforcement. The footing2 is structurally separated from the pile 1. A footing metal part 10made of a recessed seat-shaped metal (mainly steel) correspondingthereto is closely fitted into an inner surface of therecessed-jointing-portion 9 on the bottom of the footing 2, and theouter surface of the footing metal part 10 is integrally fixed andconnected to the bottom of the footing 2 via a number of anchor members11 made of steel, for fixation.

A sliding member 12 is disposed between the flat top surfaces of thepile metal part 4 fitted and fixed in the protrusive-supporting-portion3 on a side of the pile 1 and the footing metal part 10 fitted and fixedin an inside of the recessed-jointing-portion 9 on a side of the footing2, thereby building a roller bearing structure for making it possible torelatively slidingly move the joint portion of the pile head in ahorizontal direction, and an enclosing structure wherein a caulkingcompound 13 is enclosed with a sliding surface (i.e., a clearanceportion except a portion for disposing the sliding member 12) betweenthe protrusive-supporting-portion 3 on a side of the pile 1 and therecessed-jointing-portion 9 on a side of the footing 2.

For use, the sliding member 12 is adhesively bonded to a resin sheetmade of fluororesin or polyethylene resin or the like, or it is coatedwith the fluororesin or the polyethylene resin. In addition, a solidlubricating material including a carbon material and a molybdenummaterial may be applied to the sliding surface of the resin sheet.Anyway, as the sliding member 12, a material having self-lubricatingproperty is employed.

Preferably, a material employed as the caulking compound 13 is a sealantmaterial, a rubber packing or the like, having superiority in cut-off ofwater property and vibration absorbing property.

On the other hand, the pin bearing structure X is built as shown in FIG.4. In other words, the head of the pile 1 made of reinforced concrete isprovided with a spherical-supporting-portion being convex shaped, havinga spherical top surface, so as to protrude above the upper surface ofthe underground B. In an outer surface of thespherical-supporting-portion 23, a convex seat-shaped pile metal part 24corresponding thereto is fitted. An inner surface of the pile metal part24 is integrally connected to the head of the pile 1 via a number ofanchor members 25 made of steel, for fixation. On the bottom of thefooting 2 made of reinforced concrete, a concavespherical-jointing-portion 29 having a spherical top surface isdisposed, so as to correspond to the convex spherical-supporting-portion23 of the head of the pile 1 and have a greater diameter than that ofthe corresponding spherical-supporting-portion 23. In an inner surfaceof the spherical-jointing-portion 29, a footing metal part 30 beingconcave seat-shaped, corresponding thereto, is fitted. An outer surfaceof the footing metal part 30 is integrally connected to the bottom ofthe footing 2 via a number of anchor members 21 made of steel, forfixation.

Between vertically opposite spherical surfaces of the pile metal part 24on a side of the pile 1 and the footing metal part 30 on a side of thefooting 2, a sliding member 32 is interposed, thereby building the pinbearing structure for making it possible to relatively slidingly rotatethe joint portion of the pile head, and an enclosing structure wherein acaulking compound 33 is enclosed with a sliding surface (i.e., aclearance portion except a portion for disposing the sliding member 32)between the convex spherical-supporting-portion 23 on a side of the pile1 and spherical-jointing-portion 29 on a side of the footing 2.

Moreover, the pin bearing structure X has an arrangement wherein thecrushed-stone layer 7 as well as the mortar seat 6 are laminated betweenthe upper surface of the underground B and the bottom of the footing 2.Furthermore, as to the sliding member 32 and the caulking material 33,the same materials as those used in the roller bearing structure Y areemployed.

As mentioned above, a center area▭within the construction range of theupper structure A is provided with the roller bearing structure Ywherein the bottom of the footing 2 and the head of the pile 1 can berelatively slidingly moved in horizontal two dimensional directionsincluding lateral and longitudinal directions (i.e., the arrow “a”direction and the cross dots direction in FIG. 3), and the outerperiphery thereof is provided with the pin bearing structure X whereinthe bottom of the footing 2 and the head of the pile 1 can be relativelyslidingly rotated along the spherical-supporting-portion 23 and thespherical-jointing-portion 29 in all directions (i.e., the direction ofthe arrow “b” in FIG. 4). In other words, a pile foundation structurebased on a complex structure of including the roller bearing structureand the pin bearing structure is adopted, whereby a horizontal componentof earthquake motion is mainly absorbed by a sliding effect of theroller bearing structure Y. This makes it possible to decrease stressconcentration applied to the joint portion of the pile head and thebending moment which occurs on the pile 1 driven into the underground B.On the other hand, the pin bearing structure X can restrain the upperstructure A accompanied with an effect of great external forces of theearthquake motion or the like from rotating. Moreover, the pin bearingstructure X can ensure positional restoration performance of the upperstructure A after the earthquake happens.

Accordingly, even in applying a great external force such as anearthquake, the present invention can prevent the head of the pile 1 andthe footing 2 from being damaged and destroyed, thereby ensuringearthquake proofing property, and earthquake avoidable property, wherebyan amount of arrangement of reinforcement, employed as the pile 1 andthe footing 2, can be decreased so as to make a whole of the pilefoundation structure lightweight, execution can be enhanced and coststhereof can be decreased.

Furthermore, the crushed-stone layer 7 is formed on a side of the lowersurface of the footing 2 of the roller bearing structure Y for absorbingthe horizontal component and the pin bearing structure X. As a result,the pile foundation structure is isolated from the underground B,thereby exhibiting the earthquake avoidable property with the resultthat a seismic force and the lateral shaking of the upper structure areextremely reduced. Accordingly, the livability is improved, and thedamage preventive effect is further enhanced.

In addition, structurally, the caulking compound 13, 33 is enclosed withthe respective sliding surfaces between theprotrusive-supporting-portion 3 of the head of the pile 1 and therecessed-jointing-portion 9 of the bottom of the footing 2 and betweenthe convex spherical-supporting-portion 23 on a side of the pile 1 andthe concave spherical-jointing-portion 29 on a side of the footing 2.The caulking compound 13, 33 enhances the vibration absorbing property,and prevents water or the like from intruding from the outside to thesliding surface. Therefore, this can decrease corrosion of the steelmaterial as the element materials including the pile metal part 4, 24and the footing metal part 10, 30, and deterioration of the slidingmember 12, 32, and keep the sliding movement property smooth and stablefor a long time.

Furthermore, the pile foundation structure shown in the above firstembodiment is described as the complex structure wherein the pin bearingstructure X is arranged on the outer periphery of the construction rangeof the upper structure A, and the roller bearing structure Y is arrangedon the center area thereof. This structure is suitable for a casewherein the upper structure A is substantially square in a plan view,and the center of gravity is positioned in the center of theconstruction range thereof On the other hand, in case that the upperstructure A is substantially square in plan view, the weight of theupper structure A is unbalanced in the right and left of the drawing,and the center of gravity is biased and positioned on a heavier sidethereof it is preferable to adopt the complex structure as shown in FIG.5, wherein the arrangement of the roller bearing structures Y in astructure zone A1 which is the heavier side in the construction range ofthe upper structure A is different from that in a structure zone A2which is the lighter side in the construction range thereof, and the pinbearing structures X are arranged so as to surround the outer peripheryof the roller bearing structure Y in the each zone A1, A2.

Furthermore, in case that the upper structure A is large-sized to bebent in a substantial L-shape in a plan view, it is preferable to adoptthe complex structure as shown in FIG. 6. In other words, the rollerbearing structures Y in a structure zone A3 of one side of the bentportion and a structure zone A4 of the other side of the bent portionare respectively varied in the arrangement and the number thereof, andthe pin bearing structures X are arranged so as to surround the outerperiphery of the roller bearing structure Y of the each structure zoneA3, A4.

To the contrary to the pile foundation structure of the firstembodiment, it may have almost the same effect as the above to adopt thecomplex structure as shown in FIG. 7, wherein the each roller bearingstructure Y is arranged on the outer periphery of the construction rangeof the upper structure A and the each pin bearing structure X isarranged on the center area thereof.

To the contrary to the pile foundation structure of the firstembodiment, it may have almost the same effect as the above to adopt thecomplex structure as shown in FIG. 7, wherein each roller bearingstructure Y is arranged on the outer periphery of the construction rangeof the upper structure A and the each pin bearing structure X isarranged on the center area thereof

FIG. 8 shows a second embodiment of the present invention. In the pilefoundation structure of the second embodiment, each rigid jointstructure Z shown by an outlined circle in FIG. 8 is adapted as a jointstructure for joining the head of the pile 1 positioned on the outerperiphery of the construction range of the upper structure A to thefooting 2 on a side of the upper structure A. On the other hand, eachroller bearing structure Y shown by a square in FIG. 8 is adopted on aside of the center area of the construction range.

In the same way as the structure illustrated in FIG. 13, a lower end ofa footing 101 (2) is mounted on a head of a pile 100 (1), and the pile100 (1) is rigidly joined to the footing 101 (2) by a reinforcing steelmember 102 (15) including a pile reinforcement and aconcrete-reinforcing bar, and concrete. Herein, references inparentheses are elements in the rigid joint structure Z of the secondembodiment.

Moreover, the roller bearing structure Y is identical to one illustratedin FIG. 3. Therefore, the detail description of the structure isomitted.

As mentioned above, the complex structure including the rigid jointstructure Z and the roller bearing structure Y is adopted. In otherwords, the center area of the construction range of the upper structureA is provided with the rigid joint structure Z, wherein the bottom ofthe footing 2 is rigidly joined to the head of the pile 1 via thereinforcing steel member and the concrete, while the outer peripherythereof is provided with the roller bearing structure Y wherein thebottom of the footing 2 and the head of the pile 1 can be relativelyslidingly moved in the horizontal two dimensional directions includinglateral and longitudinal directions (i.e., the arrow “a” direction andthe cross dots direction in FIG. 3) Accordingly, in case that theexternal force such as the earthquake motion propagated from theunderground B is applied to the upper structure A when the earthquakehappens, the rigid joint structure Z restrains the outer periphery ofthe upper structure A which moves on a larger scale than the center areathereof from horizontally moving and rotating. This can preventlivability from worsening owing to unnecessary rocking of the upperstructure A, even if the relatively small external forces such as thetraffic vibration and the wind load are applied thereto. Moreover, whenthe great horizontal component accompanied with the earthquake motion orthe like is applied thereto, the horizontal component is absorbed bymeans of the sliding effect of the roller bearing structure Y, therebymaking it possible to decrease the stress concentration applied to thejoint portion of the pile head and the bending moment occurring on thepile 1. As a result, when the great external force such as theearthquake motion is applied thereto, it is possible to prevent thejoint portion of the pile head and pile 1 itself from being damaged anddestroyed, and to exhibit the excellent earthquake avoidable property.

In the pile foundation structure according to the second embodiment, thecomplex structure has been described, wherein the outer periphery of theconstruction range of the upper structure A is provided with the rigidjoint structure Z, and the center area thereof is provided with theroller bearing structure Y. To the contrary, it may have almost the sameeffect and action as the above embodiment to adopt the complex structureas shown in FIG. 9, wherein the outer periphery of the constructionrange of the upper structure A is provided with the roller bearingstructure Y, and the center area thereof is provided with the rigidjoint structure Z.

Moreover, in case that the center of gravity is out of the center of theupper structure A so as to be biassedly positioned on one side even ifthe plan view of the upper structure A is substantially rectangular, orin case that the upper structure A is large-sized to be bent in asubstantial L-shape in a plan view, it is preferable to adopt thecomplex structure wherein the each roller bearing structure Y isarranged as shown in FIGS. 5 and 6, and the each rigid joint structure Zis arranged so as to surround the outer periphery of the roller bearingstructure Y according to the each embodiment.

FIG. 10 illustrates a third embodiment of the present invention.

In the pile foundation structure of the third embodiment, each rigidjoint structure Z shown by an outlined circle in FIG. 10 is adopted as ajoint structure for joining the head of the pile 1 positioned on thecenter area of the construction range of the upper structure A to thefooting 2 on a side of the upper structure A, while each pin bearingstructure X shown by a circle with slant bars shown in FIG. 10 isarranged on a side of the outer periphery of the construction range.

In the same way as the structure illustrated in FIG. 13 of the secondembodiment, the lower end of the footing 2 is mounted on the head of thepile 1, and the pile 1 is rigidly joined to the footing 2 with thereinforcing steel member 15 including a pile reinforcement and aconcrete-reinforcing bar, and the concrete.

In addition, the pin bearing structure X is identical to one illustratedin FIG. 4. Therefore, the detail description of the structure isomitted.

As mentioned above, the complex structure including the rigid jointstructure Z and the pin bearing structure X is adopted. In other words,the center area of the construction range of the upper structure A isprovided with the rigid joint structure Z, wherein the bottom of thefooting 2 is rigidly joined to the head of the pile 1 via thereinforcing steel member and the concrete, while the outer peripherythereof is provided with the pin bearing structure X wherein the bottomof the footing 2 and the head of the pile 1 can be relatively slidinglyrotated along the spherical-supporting-portion 23 and thespherical-jointing-portion 29 in all directions (i.e., the direction ofthe arrow “b” in FIG. 4). Accordingly, in case that the external forcesuch as the earthquake motion propagated from the underground B isapplied to the upper structure A when the earthquake happens, the rigidjoint structure Z restrains the upper structure A from rotating. Whenthe external force which is above the predetermined value is appliedthereto by the earthquake motion or the like, the stress is released bysliding rotation of the pin bearing structure X, thereby making itpossible to decrease the stress concentration applied to the jointportion of the pile head and the bending moment occurring on the pile.This can prevent the joint portion of the pile head and the pile 1itself from being damaged and destroyed. Moreover, the underground B ishorizontally moved, thereby moving the center of the gravity of theupper structure A. As a result, deformation occurs on the pile 1 inwhich the rigid joint structure Z is adopted, and vertical motion of theupper structure A occurs according to the rotation of the pile head,which is built as the pin bearing structure X. Consequently, thestructure can ensure the positional restoration performance of the upperstructure A after the earthquake happens.

Though the pin bearing structure X described in the first and thirdembodiments has an arrangement wherein the spherical-supporting-portion23 of the head of the pile 1 is shaped into convexity, and thespherical-jointing-portion 29 of the bottom of the footing 2 is shapedinto concavity, it may have the reversed arrangement wherein thespherical-supporting-portion 23 of the head of the pile 1 is shaped intoconcavity, and the spherical-jointing-portion 29 of the bottom of thefooting 2 is shaped into convexity. Then, the latter arrangement canhave the same action and effect as the former one.

As mentioned above, the pile foundation structure according to thepresent invention relates to a technique wherein a complex structurei.e., any of a roller bearing structure and a pin bearing structure, arigid joint structure and the roller bearing structure or the rigidjoint structure and the pin bearing structure, is disposed between asupporting portion of a pile head for propagating a load of an upperstructure to the underground depths, and a joint-portion of a bottom ofa footing. This can reduce stress concentration applied to the jointportion of the pile head and bending moment applied to the pile whichare accompanied with the earthquake motion, make a whole of thestructure lightweight, reduce costs, and prevent the pile and the jointportion of the pile head from being damaged or destroyed. Moreover, thisis the technique for improving the positional restoration performance ofthe upper structure A after the earthquake happens.

What is claimed is:
 1. A pile foundation structure joining a footing ofan upper structure to heads of plural piles disposed within aconstruction range of the upper structure so as to be spaced from eachother, and driven into the underground, the improvement comprising: aroller bearing structure constructed as a joint structure disposedwithin the construction of the upper structure between some of theplural piles and portions of the footing of the upper structurecorresponding thereto, wherein: a protrusive-supporting-portion having aflat top surface is disposed on a side of the head of the pile, in astate of protruding above an upper surface of the underground; arecessed-joint-portion having a flat top surface is disposed on a sideof the footing of the upper structure, so as to correspond to theprotrusive-supporting-portion and be greater than theprotrusive-supporting-portion; and a sliding member is interposedbetween the top surfaces of the protrusive-supporting-portion and therecessed-joint-portion, for relatively slidingly move a joint portion ofthe head of the pile in a horizontal direction; and a pin bearingstructure is constructed as each joint structure and disposed on theouter periphery of the roller bearing structure and between the othersof the plural piles and portions of the footing of the upper structurecorresponding thereto, wherein: a spherical-supporting-portion having aconvex or concave outer surface is disposed on a side of the head of thepile, protruding above the upper surface of the underground, aspherical-joint-portion having a concave or convex inner surface isdisposed on a side of the footing of the upper structure, so as tocorrespond to the spherical-supporting-portion and be greater than thespherical-supporting-portion; and a sliding member is interposed betweenthe outer surface of the spherical-supporting-portion and the innersurface of the spherical-joint-portion of the footing of the upperstructure, to relatively slidingly rotate the joint portion of the headof the pile.
 2. A pile foundation structure according to claim 1,wherein a crushed-stone layer for supporting the footing of the upperstructure so as to be horizontally movable, is formed between a bottomsurface of the footing of the upper structure and the upper surface ofthe underground.
 3. A pile foundation structure according to claim 1,wherein a caulking compound is enclosed with respective sliding surfacesbetween the protrusive-supporting-portion of the head of the pile andthe recessed-joint-portion, constructed as the roller bearing structure,and between the spherical-supporting-portion of the head of the pile andthe spherical-joint-portion, constructed as the pin bearing structure.4. A pile foundation structure according to claim 1, wherein metal partsmade of metal are respectively closely fitted into an outer surface ofthe protrusive-supporting-portion on a side of the head of the pile andan inner surface of the recessed-joint-portion of the bottom portion ofthe footing, constructed as the roller bearing structure; and the outersurface of the spherical-supporting-portion on a side of the head of thepile and the inner surface of the spherical-joint-portion, constructedas the pin bearing structure, and the metal parts are integrallyconnected to the head of the pile and the bottom of the footing viaanchor members.
 5. A pile foundation structure according to claim 1,wherein the sliding member is made of a material being self-lubricative.